Absorbent articles, such as disposable diapers, training pants, and adult incontinence undergarments, absorb and contain body exudates. Some absorbent articles, like diapers, contain superabsorbent polymer material. Superabsorbent polymers are typically present in an absorbent structure such as the absorbent core of the absorbent articles in the form of particles. Superabsorbent polymer particles are able to absorb liquid and swell when coming into contact with liquid exudates. However, not all categories of superabsorbent polymer particles and of absorbent structures are equally suitable for use in an absorbent article.
It is generally known that in order to have absorbent articles comprising superabsorbent polymer particles which exhibit good absorbing and containing functions, specific technical requirements should be fulfilled by the superabsorbent polymer particles and the absorbent structures in which the superabsorbent polymer particles are contained.
The superabsorbent polymer particles and the absorbent structure should also highly permeable to liquid. A poor permeability of the superabsorbent polymer particles or the structure containing them may induce leakage of the absorbent article due to gel blocking. Gel blocking can occur in the absorbent structure when swelling superabsorbent polymer particles block the void spaces between the particles. In such a case, the liquid exudates cannot or very slowly reach underneath layers of superabsorbent polymer particles disposed in the absorbent structure. The liquid exudates remain on the surface of the absorbent structure and may therefore leak from the diaper.
The permeability of the superabsorbent polymer particles has typically been characterized in the prior art by measuring the SFC (Saline Flow Conductivity) of the particles. This parameter is measured at equilibrium, i.e. the measure is performed on a fully preswollen gel bed of superabsorbent polymer particles.
Similarly, the permeability of absorbent structures has also been characterized in the prior art on fully preswollen absorbent structures.
However, the inventors have now surprisingly found that superabsorbent polymer particles and absorbent structures having a high permeability measured at equilibrium do not automatically result in fast acquisition times of liquid exudates into the absorbent article, especially at the first gush, i.e. when the dry superabsorbent polymer particles first come into contact with liquid (i.e. when the superabsorbent polymer particles are far from reaching equilibrium).
The present disclosure therefore provides a test method to determine the time it takes for dry superabsorbent polymer particles to reach a certain liquid uptake, as well as to determine the dynamic permeability of superabsorbent polymer particles or of absorbent structures containing them. Hence, it is possible to use this method in order to determine the behavior of the superabsorbent polymer particle or of absorbent structures containing them upon their first contact with liquid. The method thus enables an easier selection of the suitable superabsorbent polymer particles or absorbent structures containing them for use in absorbent articles.